Telephone repeating instrument.



C. D. LANNING.

TELEPHONE REPEATING INSTRUMENT.

Patented Dc. 18,1917.

3 SHEETSSHEET 1 APPLICATION FILED AUG-2. I911.

Inventor Chartesllbauru' C. D. LANNING.

TELEPHONE REPEATING INSTRUMENT.

APPLICATION FILED AUG-2. 1911.

1,250,192. Patented Dec. 18, 1917.

3 SHEETS-SHEET 2- witnesses Invania r Charleslllmwmzng, aa/pfi'fim. a?

C. U. LANNING.

Patented Dec. 18, 1917.

3 SHEETS-SHEET 3.

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?5 O is) 9 It I A Zfivhzessea. ventar' wv/%@ WeamsDLanuiu UNITED STATESPATENT OFFICE.

CHARLES I). LANNING, OF BOSTON, MASSACHUSETTS, ASSIGNOR TO ODIN B.ROBERTS, TRUSTEE, OF BOSTON, MASSACHUSETTS.

TELEPHONE REPEATING INSTRUMENT.

Specification of Letters Patent.

Patented Dec. 18, 1917.

Continuation of applications Serial No. 44,049, filed January 21, 1901,and Serial No. 291,530, filed December To all whom it may concern:

Be it known that 1, CHARLES D. LANNING, a citizen of the United States,and a resident of Boston, in the county of Suffolk and Commonwealth ofMassachusetts, have invented an Improvement in Telephone RepeatingInstruments, of which the follow ing description, in connection with theaccompanying drawings, is a specification, like characters on thedrawings representing like parts.

My invention has reference to instruments for repeating and therebyrelaying or reinforcing telephone voice currents; and particularly tothe class of such instruments embodying an electro-magnetic receivingelementand a variable resistance transmitting element controlled by suchreceiving element, the receiving element being con nected into theincoming line and a transmitting circuit operatively controlled by saidvariable resistance device being connected to an outgoing line.

In the operation of such an instrument it is obvious that there are anumber of successive transformations of energy and my invention ingeneral consists in simplifying the instrument and in so arranging itthat each cooperating part may perform its desired function withefficiency, and in connecting and arranging the parts so that there willbe as little energy loss as possible in the various transformationsnecessarily taking place and so that reproduction of the voice-currentwave may be accomplished with the minimum distortion thereof; wherebythe desired object may be efficiently attained; such object being theestablishing of a new and stronger current in which the wave form of thereceived current shall be reproduced as accurately as possible.

I have illustrated my invention in the annexed drawings which are madein the various figures on slightly different scales from workingapparatus of which the principal portions of the receiving andtransmitting devices e. the receiving magnet and the transmittingmicrophone) are parts of the usual commercial transmitter and receiverrespectively as used on commercial telephone lines; which will indicatein eneral the size and proportion of parts that find it advantageous toemploy.

This application filed August 2, 1911.

Serial No. 641,947.

In the drawings Figure 1 is a plan View of one embodiment of myinvention and Fig. 2 is an elevation partially in section of theapparatus shown in Fig. 1.

Fig. 3 is a plan view of another embodiment of my inventionsubstantially similar to Fig. 1 except that some of the auxiliary partstherein illustrated are omitted.

Fig. 4 is an elevation partly in section of the apparatus shown in Fig.3.

Fig. 5 illustrates another and slightly different embodiment of myinvention being substantially similar to what is shown in Fig. 1 exceptthat the position of some of the cooperative vibratory parts isrelatively reversed.

Fig. 6 is an elevation partly in section of the apparatus shown in Fig.5.

Referring to the drawings in general it will be seen that they allembody a similar mechanism for correlating the receiving andtransmitting elements of the repeater. The receiving element in eachcase g is the usual permanent magnet with soft iron pole-pieces asemployed in the commercial receiver, with its windings, y, 1 mounted onsoft iron pole-pieces attached to the permanent magnet as clearly shownin plan in Figs. 1 and 3.

The magnet winding is placed in series with the receiving circuitthrough 11, 2, coils 3 y, 3 and o. This form of magnet is adopted forits simplicity and demonstratec efficiency. The windings are of theusual type with approximately 100 ohms resistance. The permanent magnetprovides an initial field as usual, acting upon the related armaturewhereby the magnet is responsive differentially, and therebycumulatively, as usual to the opposite phases of the receivedalternating line current.

In place of the provision of this initial field by the permanent magnet,there might be provided additional windings for the creation of thisinitial field by a separate battery-energized circuit of the magnet;suchmeans having been many times disclosed in the published art relatingto telephone repeaters and providing in some instances a useful meansfor regulating the strength of th s initial flux of the receiving magnetwhereby its initial strain upon the armature attached to the operatedmicrophone may be regulated. In place thereof I provide in the variousforms shown a means for regulating the gap between the magnet andrelated armature as will be described in detail in connection with theseparate figures, but either of such means may be employed.

Operatively the magnet is fixedly mount ed on a supporting block orpediment Z". In the field of the magnet is supported a block armature pby rigid and central attachment to the vibratory electrode of themicrophone. The provision of the armature in non-diaphragmatic form,that is,confin ing its function entirely to that of a responsive magnetic member, secures the maximum etli ciency in the armature as part ofthe magnetic circuit. Not being limited in dimen sions by considerationsof flexibility it may be made as thick as desired and built in any otherestablished manner, such as being provided with laminations orotherwise. By means of the adjusting mechanism as shown the air gapbetween the armature and magnet may also be established 'ata minimumdistance and thus, with a magnet of ellicient design, an armature soconstructed and proportioned as to be more etlicient magnetically thanwhen limited in thickness as in diaphragms, and an air gap limitedto'the smallest practicable distance, the energizing windingsbeing alsoas near the ends of the pole-pieces as practicable, a magnetic circuitand a receiving magnetic device of great efficiency is secured. I I

In all the forms shown the said block armature is rigidly and centrallyattached to the vibratory electrode of the microphone. This microphoneis provided in the form of what is known as the solidback micro phone asemployed for some time past in the. commercial transmitter in the Bellservice. This microphone is shown in general outline in Figs. 1, 2, '5and G, and in detail in'Figs. 3 and 4-. It comprises, as is wellunderstood in the art, a chamber having in the rear portion aplatecarbon electrode. The front electrode is formed as part of a compositediaphragm-electrode structure; this structure being clamped upon thewalls of the chamber in such manner that the diaphragmelectrodestructure is maintained, preferably through granular carbonheld in saidchamber between the front and back electrodes, in electrical connectionwith said back electrode. The diapln'agm-electrode structure is formedso that=when assembled it'has an interior plate carbon electrode and anexterior clamping member, an annular diaphragm preferablyv of micaclamped therebetween and said diaphragm being clamped upon the walls-ofthe chamher as above described; all'as well understood in the art and asdisclosed in a prior United States patent to A. lV-hite.

In all the forms of apparatus illustrated being,

herein, said microphone is shown fixedly mounted on a pedestal. orsupport, which is, a-preferable but not essential construction.

It will be seen, therefore, that the armature member is separated in allforms from the vibratory electrode and diaphragm elements and also thatthe sin le diaphragm of the solid-back electrode structure constitutesthe only diaphragmatic member involved in the vibratory operation of thecon nccted armature and vibratory electrode. In this way not only is thearmature provided in a design calculated to secure the greatestefficiency thereof but the vibratory,electrmt of the microphone ispreserved in form, assembled, so that its freedom of movement andaccuracy in performing its vibratory function, cooperating with thevarying strain of the magnet, is not impaired. lVhere the vibratoryelectrode is subject to'the control of more than one diaphragmaticmember great difliculty is found in maintaining the diaphragms inparallel alinement and'concentrically arranged; and unless suchcondition is preserved manifestly each diaphragm tends to restrain theaction of the other and thereby the action of the microphone is muchimpaired.

I have provided in the preferred form of instrument herein shown as inFigs. 1 and 5 an auxiliary tension member to cooperate in the regulationof vibratory actiom'noin diaphragmatic in form, so that thisdil'licult-y of adjustment and resulting impairment of microphoneoperation may be avoided and at the same time the single diaphragmmaintained as nearly as possible in an initially flat condition which isobviously its condition of greatest delicacy as related to'freedom ofvibratory movement; which auxiliary element I 'will later dc scribe.

It will be seen, therefore, that in all the forms of instrumentsillustrated in the drawings the ellici'ent character of the simplifiedrepeater instrument that I have invented resides essentially in theprovision of a receiving elcctro-magnetic element havingas a cooperativemember thereof a block armature disassociated in function from' thevibration-controlling element of the microphone or from 'the electrodeele ment or elements of the microphonegin mounting this block armatureby central and rigid attachment to the vibratory electrode; and inproviding the microphone in form where its vibratory electrode is acomposite diaphragm electrode structure, constituting the only diaphragmelement operativ'ely related to the perform-- ance by the connectedarmature andvib'ratory electrode of their vibratoryfunctions. It will beobvious that'this construction, by disassociating the repeatinginstrument 'entirely from instruments designed to respond to or toproduce audible sound, supplies a current-actuated and acurrent-reproducing instrument in a simple and efiicient form.

Referring to the drawings in detail, in Fig; 1 the receiving magnet 3 ismounted as shown upon a block pediment t which latter is mounted upon anadjusting carriage, the block t engaging the worm u so that the magnetmay be given an adjusting movement with reference to its relation to thearmature p. This worm is provided with amilled'end nut 11 and a lock nutu; the said worm u receiving a permanent and controlling end thrust fromthe interposed coil spring at one end thereof, u. In this form ofinstrument the parts are interconnect-ed sothat any increase ofattraction upon the. armature p will result in increase of pressure inthe microphone; and for that purpose the armature p is mounted, by meansof the connecting yoke g, centrally upon the vibratory electrodestructure 71 of the microphone; the said yoke being preferably made, asin the instrument shown, of aluminum so as to be as light aspracticable. There is also connected to the vibratory electrode tooppose the initial magnetic strain on the, armature as communicated tosaid vibratory electrode, the elastic 0 which is connected at its otherend to the tension adjustment means as shown comprising the worm cmounted in a pedestal as shown and carrying at its end the bracket d,supporting the hook at, the latter engaging the said elastic as stated.-Said worm e is mounted for rotative movement in said bracket d and anauxiliary rod 03 parallel to the said worm e engages said bracket drigidly so that adjustment of said worm e by turning thereof will notdisturb the alinement of the bracket (1' and hook d with reference tothe said elastic c and connected hook b on the vibratory electrodestructure.

The function of this elastic tensioning device is to assist. inpreserving the diaphragm of the diaphragm-electrode structure initiallyin a flat condition, whereby the most sensitive condition thereof issecured. To perform this function the cooperative spring or tensioningdevice must be aperiodic in character; that is, it must have the qualityinherent in diaphragms of responding accurately to the varying periodsof vibration taking place in tone production and reproduction, withoutany dominant rate of vibration inherent in its own structure. An elasticunder rectilinear extension fulfils these requirements as well or betterthan a diaphragm, whereas any coiled spring obviously tends to introduceits own rate of vibration and thereby impair other desired action. Suchan elastic, however, may have an inherent rate of vibration at rightangles to its axis of extension and for that purpose I provide the.intermediate vibration-checking member 41*, supported in contact withthe elastic 0 by means of the arm n mounted in the pedestal m and heldin position by the lock screw 07/.

I find the provision of this rectilinearly 7O extensible auxiliarytensioning device. preferably in the form o an elastic as slrm'n, is ofconsiderable advantage. The reason for this is that the action of themicrophone is well recognized to be that its variations 75 ofconductivityare the result of variations of area of contact which latterare the consequence of varying pressure which implies movement. If theentire energy communicated to the block armature could be availed of inthe form of movement-of, and pressure between the electrodes, idealefiiciency would be secured. But in order to control the movement of thevibratory electrode and connected armature some form of mechanicalvibration-controlling device is necessary in the form of instrumentsshown; and therefore part of the energy delivered to the armature mustbe expended in overcoming the resistance or inertia of this mechanicalvibration controlling device. Diaphragms constitute very sensitivesprings but their range of excursion is very limited; and upon veryslight movement either way from a flat condition their furtheradditional movement in the same direction is substantially restrained.Where, therefore, the diaphragm through its connected armature is underthe initial strain of the electro-magnet and the current phase receivedby the receiving magnet is such as to still further increase the initialstrain, it is substantially inoperative in producing further movementof, or pressure between, the electrodes, the energy being taken up indiaphragm resistance. If very large diaphragms are used for the purposeof enlarging the range of excursion, Variations or inaccuracies ofvibratory movement creep in requiring the use of damping springs uponvarious parts of the diaphragm such as those commonly employed withtransmitter diaphragms. The function of the auxiliary tensioning devicein the form shown, therefore, is to supply a tension acting against theinitial magnetic tension to keep the diaphragm of the micro phoneinitially in a substantially flat condition. The auxiliary device beingprovided as shown, is in a form having a very large range of movementrelatively to the energy spent thereon, and is the equivalent insensitiveness of a very large diaphragm. The result is that themechanical resistance or inertia of the associated microphone diaphragmand auxiliary tensioning device is less, under the varying operatingconditions, than the resistance of the diaphragm alone when initiallydistorted as would otherwise be the case. By providing the auxiliarytension and vibration-controlling device in this nected that anyincrease of attractive action" by the receiving magnet y on the armaturep operates to decreasethe conductivity or the microphone. The instrumentbeing substantially similar 'in' all respects to that shown in Figs. 1and 2 no other description will be necessary.

In Figs. 3 and i I haveshown a form of the instrument in whlch theauxiliary vibra-f tlon controlling member is omitted. In this and '6 Ihave illustrated substantially the same general arrangement of form thereceiving magnet is mounted on a fixed pediment' t, it being otherwise0on strueted 'and1ts c1rcu1t connectedasabove described 1n connectionwlth the other figures. The transn'iitting' microphone is mounted in aholder or pediment'r, which is carried in a support W, being mountedthere- 1n on a worm r prov1ded with an end milled nut-r andlock nut rwhereby the worm,

being fixedly held in'the endmembers r 0 on said support 1, may beutilized to give the microphone and" connected armature p a movementparallel with the end faces of the receiving magnet. Said support 0 inturn mounted upon the worm a carriednr the bracket to and'u", the wormto being provided w th an'end m1lled nut' a and loclrnut 10*, wherebythe whole microphone and connected armature structure may be given amovement longitudinal of the microphone axis," By these'adjusting mearnsthe microphone and connected armature may be readily brought intoanydesired position with relation to the cooperating receiving magnet andthere supported and-maintained. The microphone is connected as beforein-series with a -local battery circuit through the binding posts 4 andthe circuit connections to the induction coils as shown, the secondaryofthe induction coil being connected into the transmitting circuit asdesired to the circuitsas shown and the binding posts 7 8 p The circuitconnections in the various instruments are. indicated by similar markingin the various figures.

It will be seen that in the form illustrated in Figs. 3 and 4 theessential features of my arrangement are embodied, but preferably I'employ the'forms illustrated in the other figures and for' thereasons'above stated. 1

While I have herein shown and described for purposes of illustration onespecific form of the invention, it is to be understood that the same isnot limited to the details of construction or relative arrangement ofparts but that extensive deviations maybe made from the discloseddetails without departing from the spirit of the invention.

Claims: 1

1. A telephonic voice-current repeating instrument, comprising aninitially magnetized receiving magnet and its circuit connections; atransmitting microphone and its in 'thefield of said magnet, rigidly andcentrally attached to said diaphragm structure; together with anauxiliary vibration-controlling member for the microphone, in the formof a rectilinearly extensible member, disposed along the central axis ofvibration of the microphone diaphragm, extended by means of anattachment to an abutment and to the associated armature and vibratoryelectrode, and opposing the magnetic pull on the armature; saidauxiliary tension member, as related to the said diaphragm member,having relatively large elastic limits and having a low inherent rate ofvibra tion.

2. A telephonic voice-current repeating instrument, comprising-aninitially magnetized receiving'magnet and its circuit connections;'atransmitting microphone and its circuit connections, embodying astationary rear electrode, an opposed electrode inthe form of asingle,peripherally-clamped, nonmagnetic, diaphragmatic, compositeelectrode-diaphragm structure, electrically related to said stationaryrear electrode, with the central axis of vibratory movement of saiddiaphragm-electrode structure substantially coincident with the centralline of pull of said magnet; and a rigid block armature in the field ofsaid magnet, rigidly and contrally attached to said diaphragm structure;together with an auxiliary vibration-controlling member for themicrophone, in the form of a rectilinearly extensible member, disposedalong the central axis of vibration of the microphone diaphragm,extended by means of'an attachment to an abutment and to the associatedarmature and vibratory electrode, and opposing the magnetic pull on thearmature; said auxiliary tension member as related to the said diaphragmmember having relatively large elastic limits and a low inherent rate ofvibration; said auxiliary tension member being non-metallic.

3. A telephonic voice-current repeating instrument, comprising aninitially magnetized receiving magnet and its circuit connections; atransmitting microphone and its circuit connections, embodying astationary rear electrode, an opposed electrode in the form of a single.peripherally-clamped, nonmagnetic, diaphragmatic, compositeelectrode-diaphragm structure, electrically related to said stationaryrear electrode, with the central axis of vibratory movement of saiddiaphragm-electrode structure substantially coincident with the centralline of pull of said magnet; and a rigid block armature in the field ofsaid magnet, rigidly and centrally attached to said diaphragm structure;together With an auxiliary vibration-controlling member for themicrophone, in the form of a rectilinearly extensible member, disposedalong the central axis of vibration of the microphone diaphragm,extended by means of an attachment to an abutment and to the associatedarmature and vibratory electrode, and opposing the magnetic pull on thearmature; said auxiliary tension member, as related to the saiddiaphragm member, having relatively'large elastic limits and a lowinherent rate of vibration; said auxiliary tension member being furtherin the form of a stretched rubber strip.

4. A telephonic voice-current repeating instrument, comprising aninitially magnetized receiving magnet and its circuit connections; atransmittitng microphone and its circuit connections, embodying astationary rear electrode, an opposed electrode in the form of a single,peripherallycla1nped non-magnetic diaphragmatic, compositeelectrode-diaphragm structure, electrically related to said stationaryrear electrode, with the central axis of vibratory movement of saiddiaphragin-electrode structure substantially coincident with the centralline of pull of said magnet; and a rigid block armature in the field ofsaid magnet, rigidly and centrally attached to said diaphragm structure;together with an auxiliary vibration-controlling member for themicrophone, in the form of a rectilinearly extensible member, disposedalong the central axis of vibration of the microphone diaphragm, extended by means of an attachment to an abutment and to the associatedarmature and vibratory electrode, and opposing the magnetic pull on thearmature; said auxiliary tension member, as related to the saiddiaphragm member, having relatively large elastic limits and a lowinherent rate of vibration; said auxiliary tension member having meansto damp the vibration across its axis of extension.

In testimony whereof, I have signed my name to this specification, inthe presence of two subscribing witnesses.

CHARLES D. LANNING.

Vitnesses THOMAS B. Boo'rn, ROBERT H. KAMMLER.

Copies of this patent may be obtained for five cents each, by addressingthe Commissioner of Patents, Washington, D. C.

